Actuator array and method for the manufacture thereof

ABSTRACT

An array of M×N electrodisplacive actuators is prepared by: 
     (1) forming a multilayered ceramic structure having M layers of a first conductive metallization and M+1 layers of an electrodisplacive material; 
     (2) obtaining a composite ceramic wafer by slicing the multilayered ceramic structure in a direction normal to the layers of the first conductive metallization; 
     (3) providing a plurality of regularly spaced horizontally directional trenches running parallel to each other wherein each of the trenches is located at an equidistance from two adjacent layers of the first conductive metallization; 
     (4) depositing a second conductive metallization; 
     (5) preparing N-1 regularly spaced vertically directional cuts on the composite ceramic wafer prepared using steps (3) and (4) to thereby obtain the array of M×N electrodisplacive actuators.

FIELD OF THE INVENTION

The present invention relates to an optical projection system; and, more particularly, to an actuator array and a novel method for manufacturing same for use in the system.

BACKGROUND OF THE INVENTION

Among the various video display systems available in the art, an optical projection system is known to be capable of providing a high quality display in a large scale. In such an optical projection system, light from a lamp is uniformly illuminated onto, e.g., an array of M×N mirrors. The array of M×N mirrors is mounted on an array of actuators which includes a corresponding number, i.e., M×N, of actuators such that each of the mirrors is coupled with each of the actuators. The actuators are made of an electrodisplacive material such as piezoelectric or electrostrictive material which deforms in response to an electric field applied thereto.

When a reflected light beam from each of the mirrors is incident upon an aperture of a baffle, by applying an electrical signal to each of the actuators, the relative position of each of the mirrors to the incident light beam can be altered, thereby causing a deviation in the optical path of the reflected beam from each of the mirrors. As the optical path of each of the reflected beams is varied, the amount of light reflected from each of the mirrors which passes through the aperture is changed, thereby modulating the intensity of the beam. The modulated beams through the aperture are transmitted onto a projection screen via an appropriate optical device such as a projection lens, to thereby display an image thereon.

Each of the actuators for use in the above-described optical projection system is conventionally made of multiple layers of an electrode and an electrodisplacive material, wherein each layer of the electrode is placed between two layers of the electrodisplacive material, which renders the structure and manufacturing process of such an array of actuators rather complex and costly.

SUMMARY OF THE INVENTION

It is, therefore, a primary object of the present invention to provide an economical and simplified method for manufacturing an array of actuators having a novel structure wherein each of the actuators comprises a signal electrode, a pair of reference electrodes, and two layers of an electrodisplacive material between the signal and the pair of reference electrodes.

In accordance with one aspect of the present invention, there is provided a novel method for manufacturing an array of M×N electrodisplacive actuators, wherein M and N are integers, for use in an optical projection system, said method comprising the steps of:

(a) forming a multilayered ceramic structure having M layers of a first conductive metallization and M+1 layers of an electrodisplacive material, wherein each layer of the first conductive metallization is placed between two layers of the electrodisplacive material;

(b) slicing said multilayered ceramic structure in a direction normal to the layers of the first conductive metallization resulting in a composite ceramic wafer having a flat surface, wherein the electrodisplacive material is evenly separated in a horizontal direction by said M layers of the first conductive metallization;

(c) providing on the entirety of said flat surface of said composite ceramic wafer M+1 regularly spaced horizontally directional trenches wherein each of said trenches has a pair of side surfaces and a bottom surface, runs parallel to each other, is located at an equidistance from two adjacent layers of the first conductive metallization and is separated from each other by a barrier having a top surface;

(d) constructing a composite ceramic body by forming a second conductive metallization on said side and bottom surfaces of each of said trenches; and

(e) preparing N-1 regularly spaced vertically directional cuts on said composite ceramic body to thereby obtain the array of M×N electrodisplacive actuators.

In accordance with another aspect of the present invention, there is provided an array of M×N actuators wherein each of the M×N actuators comprises a pair of layers of an electrodisplacive material, a layer of a first conductive metallization located between the pair of layers of the electrodisplacive material, and a pair of layers of a second conductive metallization on the external sides, respectively, of said pair of layers of the electrodisplacive material. In the actuator array, the first and the second conductive metallization layers function as the signal and the reference electrodes, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, wherein FIGS. 1A to 1I illustrate the steps used in constructing an array of M×N electrodisplacive actuators in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the present invention, the method for manufacturing the inventive array of M×N electrodisplacive actuators begins with the preparation of a multilayered ceramic structure 10, having M layers of a first conductive metallization 13_(M) and M+1 layers 11_(M+1) of an electrodisplacive material, e.g., lead magnesium niobate, wherein each layer of the first conductive metallization 13_(M) is placed between two layers of the electrodisplacive material as shown in FIG. 1A. The layers of the first conduction metallization 13_(M) are comprised of platinum(Pt), or palladium(Pd) or palladium/silver(Pd/Ag). The multilayered ceramic structure shown in FIG. 1A can be obtained by utilizing a conventional method well known in the art for manufacturing multilayered ceramic capacitors. In the case of an array of piezoelectric actuators, there is an additional constraint: that is, the multilayered structure 10 must be poled before proceeding to a next step, by applying an electric field in a direction normal to the plane of the layers of the first conductive metallization 13_(M).

Thereafter, as shown in FIG. 1B, by slicing the multilayered structure 10 in a direction normal to the layers of the first conductive metallization 13_(M), there is formed a composite ceramic wafer 15 having a flat surface 12, wherein the electrodisplacive material is evenly separated by M layers of the first metallization 13_(M).

In the subsequent step, the flat surface 12 is covered with a thin layer 16 of a polymer such as photoresist as shown in FIG. 1C.

Thereafter, as shown in FIGS. 1D and 1E, there are formed, on the entire flat surface 12 covered with the thin polymeric layer 16, M+1 regularly spaced horizontally directional trenches 20_(M+1) of an identical size, having substantially square edges, running parallel to each other, wherein each of the trenches 20_(M+1) has two side surfaces 21, 22, and a bottom surface 23, resulting in a trenched ceramic wafer 25. Furthermore, each of the trenches 20_(M+1) is located at an equidistance from two adjacent layers of the first conductive metallization 13_(M) and is separated by a barrier 26 having its top surface 27 covered with the thin polymeric layer 16. FIG. 1D represents the perspective view of the trenched ceramic wafer 25; and FIG. 1E, the cross-sectional view thereof.

As shown in FIGS. 1G and 1H, a second conductive metallization 32, comprising either silver (Ag) or aluminum (Al), is formed on the side surfaces 21, 22 and the bottom surface 23 of the trenches 20_(M+1), by first depositing a metallic layer 29, comprising either silver (Ag) or aluminum (Al), on the entire top surface of the shaped ceramic wafer 25 including the thin polymeric layer 16 on the top surface 27 of the barriers 26, the side surfaces 21, 22 and the bottom surface 23 of the trenches 20_(M+1) as shown in FIG. 1F, and then removing the metallic layer 29 formed on the thin polymeric layer 16 by dissolving the latter using an appropriate solvent, e.g., acetone, resulting in a ceramic body 30. FIG. 1F illustrates the cross sectional view of the shaped ceramic wafer 25 after the top surface thereof has been covered with the second metallic layer 29; FIG. 1G represents the cross sectional view of the ceramic body 30; and FIG. 1H, the perspective view thereof.

The metallic layer 29 is obtained by using such a conventional technique as sputtering or thermal evaporation.

In the subsequent step, there are made, on the ceramic body 30, N-1 regularly spaced vertically directional cuts 34₋₁, resulting in an array of M×N electrodisplacive actuators 33 as shown in FIG. 1I.

The array of electrodisplacive actuators 33 is then mounted on a substrate such that the first and the second conductive metallizations 13_(M), 32 function as the signal and the reference electrodes, respectively; and, therefore, the first conductive metallization 13_(M) is connected to a driver and the second conductive metallization 32 is interconnected to a common ground potential(not shown).

When a voltage is applied between the first and the second conductive metallizations 13_(M) and 32, the electrodisplacive material located between them will deform in a direction determined by the polarity of the voltage.

In order for the array 33 shown in FIG. 1I to be used as an actuated mirror array in an optical projection system, said mirrors must be attached together.

In this connection, there is disclosed a method for attaching the mirrors on such an array of actuators in a copending, commonly owned application, U.S. Ser. No. , entitled "MIRROR ARRAY AND METHOD FOR MANUFACTURE THEREOF", which is incorporated herein by reference.

While the present invention has been shown and described with reference to the particular embodiments, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims. 

What is claimed is:
 1. A method for manufacturing an array of M×N electrodisplacive actuators for use in an optical projection system, said method comprising the steps of:(a) forming a multilayered ceramic structure having M layers of a first conductive metallization and M+1 layers of an electrodisplacive material, wherein each layer of the first conductive metallization is placed between two layers of the electrodisplacive material; (b) slicing said multilayered ceramic structure in a direction normal to said layers of the first conductive metallization, resulting in a composite ceramic wafer having a flat surface, wherein the electrodisplacive material is evenly separated in a horizontal direction by said M layers of the first conductive metallization; (c) providing on the entirety of said flat surface of the composite ceramic wafer M+1 regularly spaced horizontally directional trenches, wherein each of the trenches runs parallel to each other, is located at an equidistance from two adjacent layers of the first conductive metallization, is separated from each other by a barrier having a top surface, and has a pair of side surfaces and a bottom surface; (d) constructing a composite ceramic body by forming a second conductive metallization on said side and bottom surfaces of each of the trenches; and (e) preparing N-1 regularly spaced vertically directional cuts on the composite ceramic body to thereby obtain the array of M×N electrodisplacive actuators.
 2. The method claim 1, wherein said actuators are comprised of a piezoelectric material.
 3. The method of claim 2, wherein said multilayered ceramic structure in step (a) is poled.
 4. The method of claim 1, wherein the first conductive metallization in step (a) is comprised of platinum, or palladium or palladium/silver.
 5. The method of claim 1, wherein said trenches are formed in step (c) after said flat surface in step (b) has been completely covered with a thin layer of a polymer.
 6. The method of claim 1, wherein the second conductive metallization in step (d) is comprised of aluminum or silver.
 7. The method of claim 6, wherein the second conductive metallization in step (d) is also formed on the top surface of the barrier referred to in step (c).
 8. The method of claim 7, wherein the second conductive metallization formed on the top surface of the barrier is removed by dissolving said thin polymeric layer. 